MR compatible rotating anode x-ray tube

Abstract

An apparatus for use in a magnetic resonance (MR) system, which generates an external MR magnetic field, is provided. A rotor comprises a rotor shaft with an axis along a length of the rotor shaft and a plurality of coils on the rotor shaft. A housing supports and surrounds the rotor, where a part of the housing surrounds sides of the rotor and where the part of the housing surrounding sides of the rotor is magnet free. A mount allows for the mounting of the housing to the MR system in a location where the MR system provides a magnetic field, wherein a component of the MR magnetic field that is perpendicular to the axis of the rotor shaft is at least 100 Gauss. An active timer applies a voltage to the plurality of coils with alternating polarity. Contacts provide an electrical connection between the active timer and the plurality of coils.

1. An apparatus for use in a magnetic resonance (MR) system, which generates an external MR magnetic field, comprising:
 a rotor, comprising:
 a rotor shaft with an axis along a length of the rotor shaft; and 
 a plurality of coils on the rotor shaft; 
 
 a housing supporting and surrounding the rotor, wherein a part of the housing surrounds sides of the rotor, wherein the part of the housing surrounding sides of the rotor is magnet free; 
 a mount for mounting the housing to the MR system in a location where the MR system provides a magnetic field, wherein a component of the MR magnetic field that is perpendicular to the axis of the rotor shaft is at least 100 Gauss; 
 an active timer for applying a voltage to the plurality of coils with alternating polarity; and 
 contacts for providing an electrical connection between the active timer and the plurality of coils. 
 
     
     
       2. The apparatus, as recited in  claim 1 , wherein the contacts are vacuum contacts. 
     
     
       3. The apparatus, as recited in  claim 2 , further comprising a sensor for measuring rotor position. 
     
     
       4. The apparatus, as recited in  claim 3 , further comprising an anode connected to the rotor, wherein the rotor rotates the anode. 
     
     
       5. The apparatus, as recited in  claim 4 , further comprising an e-beam generator spaced apart from the anode. 
     
     
       6. The apparatus, as recited in  claim 5 , further comprising a plurality of shielding magnets spaced around a path between the e-beam generator and the anode. 
     
     
       7. The apparatus, as recited in  claim 6 , further comprising:
 an external magnetic field sensor; 
 a controller connected to the external magnetic filed sensor and the plurality of shielding magnets, wherein the controller receives a signal from the external magnetic field sensor related to the strength of the external magnetic field and controls the plurality of shielding magnets according to the strength of the external magnetic field. 
 
     
     
       8. The apparatus, as recited in  claim 7 , wherein the active timer is a 3-phase DC motor active timer. 
     
     
       9. The apparatus, as recited in  claim 8 , wherein the contacts are brushless contacts. 
     
     
       10. The apparatus, as recited in  claim 3 , wherein the sensor is a Hall sensor system. 
     
     
       11. The apparatus, as recited in  claim 3 , wherein the active timer applies voltage to the plurality of coils based on the measured rotor position in relation to the external MR magnetic field. 
     
     
       12. The apparatus, as recited in  claim 3 , wherein the sensor is a back EMF control system. 
     
     
       13. The apparatus, as recited in  claim 1 , wherein the active timer applies voltage to the plurality of coils based on the measured rotor position in relation to the external MR magnetic field. 
     
     
       14. An x-ray tube for use in a magnetic resonance (MR) system, which generates an external MR magnetic field, comprising:
 an anode; 
 a motor for rotating the anode; 
 a cathode is spaced apart from the anode; 
 an external magnetic field sensor that measures the external MR magnetic field; 
 a plurality of active shielding magnets spaced surrounding a path from the cathode to the anode; 
 a controller connected to the external magnetic field sensor and the plurality of active shielding magnets. 
 
     
     
       15. The x-ray tube, as recited in  claim 14 , wherein the controller comprises computer readable media with computer readable code for using a signal from the external magnetic field sensor and adjusting a magnetic field produced by the plurality of active shielding magnets according to the signal from the external magnetic field sensor. 
     
     
       16. The x-ray tube, as recited in  claim 15 , wherein the active shielding magnets are coils. 
     
     
       17. An x-ray tube for use in a magnetic resonance (MR) system, which generates an external MR magnetic field, comprising:
 an anode; 
 a motor for rotating the anode, comprising:
 a rotor, comprising:
 a rotor shaft with an axis along a length of the rotor shaft; and 
 a plurality of coils on the rotor shaft; 
 
 a housing supporting and surrounding the rotor, wherein a part of the housing surrounds sides of the rotor, wherein the part of the housing surrounding sides of the rotor is magnet free; 
 a mount for mounting the housing to the MR system in a location where the MR system provides a magnetic field, wherein a component of the MR magnetic field that is perpendicular to the axis of the rotor shaft is at least 100 Gauss; 
 an active timer for applying a voltage to the plurality of coils with alternating polarity; and 
 contacts for providing an electrical connection between the active timer and the plurality of coils; and 
 
 a cathode spaced apart from the anode. 
 
     
     
       18. The x-ray tube, as recited in  claim 17 , further comprising:
 an external magnetic field sensor that measures the external MR magnetic field; 
 a plurality of active shielding magnets spaced surrounding a path from the cathode to the anode; and 
 a controller connected to the external magnetic field sensor and the plurality of active shielding magnets.